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From: Max Filippov <>
To: "Takayuki 'January June' Suwa" <>
Cc: GCC Patches <>
Subject: Re: [PATCH v2] xtensa: Make register A0 allocable for the CALL0 ABI
Date: Sat, 22 Oct 2022 00:26:43 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Fri, Oct 21, 2022 at 3:46 PM Takayuki 'January June' Suwa
<> wrote:
> This patch offers an additional allocable register by RA for the CALL0
> ABI.
> > Register a0 holds the return address upon entry to a function, but
> > unlike the windowed register ABI, it is not reserved for this purpose
> > and may hold other values after the return address has been saved.
>   - Xtensa ISA Reference Manual,
>                    8.1.2 "CALL0 Register Usage and Stack Layout" [p.589]
> gcc/ChangeLog:
>         * config/xtensa/ (xtensa_conditional_register_usage):
>         Remove register A0 from FIXED_REGS if the CALL0 ABI.
>         (xtensa_expand_epilogue): Change to emit '(use (reg:SI A0_REG))'
>         unconditionally after restoring callee-saved registers for
>         sibling-call functions, in order to prevent misleading that
>         register A0 is free to use.
> ---
>  gcc/config/xtensa/ | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)

Regtested for target=xtensa-linux-uclibc, no new regressions.
Committed to master.

-- Max

      reply	other threads:[~2022-10-22  7:26 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <>
2022-10-21  2:58 ` [PATCH] " Takayuki 'January June' Suwa
2022-10-21  5:49   ` Max Filippov
2022-10-21 22:46     ` [PATCH v2] " Takayuki 'January June' Suwa
2022-10-22  7:26       ` Max Filippov [this message]

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